build system: Back out on error at libdep stage
Tool for preparing a single 3rd-party port

Issue #1082
Build-system support for ported 3rd-party code

The new 'select_from_ports' function allows a target description file to
query the path to an installed port. All ports are stored in a central
location specified as CONTRIB_DIR. By default, CONTRIB_DIR is defined
as '<genode-dir>/contrib'. Ports of 3rd-party source code are managed
using the tools at '<genode-dir>/tool/ports/'.

Issue #1082
tool/prepare.mk: Switch directories silently
Build-system support for creating host tools
Migrate libports to new ports-management mechanism

Issue #1082
Migrate base-okl4 to new ports management

Issue #1082
Migrate base-nova to new ports management

Issue #1082
Migrate dde_oss to new ports management

Issue #1082
Migrate ports to new ports management (WiP)

Issue #1082
Temporarily disable hash checks

...until the transition to the new ports management is complete.
doc: Description of HOST_TOOLS mechanism
doc: Uniform markup of the build-system manual

Use _italic_ for path names rather than 'verbatim'. Because path names
tend to be quite long, the overly use of verbatim makes paragraphs hard
to read.
doc: Update link to gosh
Volatile_object: align the embedded object

The space for the embedded object needs to be natively aligned to avoid
alignment errors on ARM.

Fixes #1149.
fixup prepare_port (allow symlinks in repos/)
fixup okl4 (remove commented-out code)
fixup prepare_ports (sha1sum format fix)

Apparently some versions of sha1sum expect exactly two spaces between
the hashsum and the filename when doing the check (-c).
fixup build (use <port-name>-<fingerprint> as port dir)
fixup prepare_port (use <port-name>-<fingerprint> as port dir)